title: Ubiquitin-proteasome system impairment caused by a missense cardiac myosin-binding protein C mutation and associated with cardiac dysfunction in hypertrophic cardiomyopathy.
abstract: The ubiquitin-proteasome system is responsible for the disappearance of truncated cardiac myosin-binding protein C, and the suppression of its activity contributes to cardiac dysfunction. This study investigated whether missense cardiac myosin-binding protein C gene (MYBPC3) mutation in hypertrophic cardiomyopathy (HCM) leads to destabilization of its protein, causes UPS impairment, and is associated with cardiac dysfunction. Mutations were identified in Japanese HCM patients using denaturing HPLC and sequencing. Heterologous expression was investigated in COS-7 cells as well as neonatal rat cardiac myocytes to examine protein stability and proteasome activity. The cardiac function was measured using echocardiography. Five novel MYBPC3 mutations -- E344K, DeltaK814, Delta2864-2865GC, Q998E, and T1046M -- were identified in this study. Compared with the wild type and other mutations, the E334K protein level was significantly lower, it was degraded faster, it had a higher level of polyubiquination, and increased in cells pretreated with the proteasome inhibitor MG132 (50 microM, 6 h). The electrical charge of its amino acid at position 334 influenced its stability, but E334K did not affect its phosphorylation. The E334K protein reduced cellular 20 S proteasome activity, increased the proapoptotic/antiapoptotic protein ratio, and enhanced apoptosis in transfected Cos-7 cells and neonatal rat cardiac myocytes. Patients carrying the E334K mutation presented significant left ventricular dysfunction and dilation. The conclusion is the missense MYBPC3 mutation E334K destabilizes its protein through UPS and may contribute to cardiac dysfunction in HCM through impairment of the ubiquitin-proteasome system.
authors.affiliation: Division of Regenerative Medicine and Therapeutics, Institute of Regenerative Medicine and Biofunction, Tottori University Graduate School of Medical Science, Yonago, Japan.
authors.forename: Udin
authors.initials: U
authors.lastname: Bahrudin
authors.forename: Hiroko
authors.initials: H
authors.lastname: Morisaki
authors.forename: Takayuki
authors.initials: T
authors.lastname: Morisaki
authors.forename: Haruaki
authors.initials: H
authors.lastname: Ninomiya
authors.forename: Katsumi
authors.initials: K
authors.lastname: Higaki
authors.forename: Eiji
authors.initials: E
authors.lastname: Nanba
authors.forename: Osamu
authors.initials: O
authors.lastname: Igawa
authors.forename: Seiji
authors.initials: S
authors.lastname: Takashima
authors.forename: Einosuke
authors.initials: E
authors.lastname: Mizuta
authors.forename: Junichiro
authors.initials: J
authors.lastname: Miake
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Shirayoshi
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kitakaze
authors.forename: Lucie
authors.initials: L
authors.lastname: Carrier
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hisatome
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D019556:COS Cells; D002312:Cardiomyopathy, Hypertrophic / Q000473:pathology*; D002352:Carrier Proteins / Q000235:genetics*; D002522:Chlorocebus aethiops; D002851:Chromatography, High Pressure Liquid; D004452:Echocardiography; D006801:Humans; D007564:Japan; D008875:Middle Aged; D020125:Mutation, Missense; D009206:Myocardium / Q000473:pathology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D051381:Rats; D017422:Sequence Analysis, DNA; D025801:Ubiquitin / Q000378:metabolism*; D000099163:Myosin Binding Protein C
chemical_list: D002352:Carrier Proteins; D046988:Proteasome Endopeptidase Complex; D025801:Ubiquitin; D000099163:Myosin Binding Protein C